Menstrual synchrony- is period syncing real or it's just a myth?

Can this be real? or is it just a myth?.

Period syncing or menstrual synchrony also known as the McClintock effect is based on the theory that when a woman comes in close physical contact with another woman, their pheromones- chemicals created by the body that affect our social and sexual behaviors- influence each other so that eventually, their monthly cycles align.

Anecdotally, some women accept that period syncing is real, however, the medical literature doesn't have a solid case to prove that it happens. Or does not.

The first scientific evidence of period syncing came about in 1971 with the McClintock study when a researcher from Harvard University, Martha McClintock studied the menstrual cycles of a group of 135 women living in a college dorm. After six months, this study found that the women in close proximity had their periods start three to seven days apart while those who were not in close proximity- used as the control- started their periods five to 15 days apart. This study found that there seemed to be a relationship between menstrual cycle and spending extended amounts of time with other women.

Since a scientific study supports the concept of menstrual synchrony, it's supposed to be true, right? Not really. Some flaws were found in Mcclintock's study, therefore its findings were disregarded.

In 2006, another study collected data from 186 women living in groups in a dorm in China. This study asserted that women do not sync their menstrual cycles and any syncing that occurs is purely coincidental.

A period tracking app, Clue teamed up with Oxford University to conduct a large study on over 1500 women. Data collected from these women demonstrated that it is unlikely that women can disrupt each other's cycles by being in close proximity.

A 2017 study kept the idea of period syncing alive by pointing out that 44% of the participants of the study that were living with other women experienced period synchrony.

The truth about period syncing might never be discovered. One of the reasons why is because scientists don't know for sure if the pheromones on which the theory of menstrual synchrony is based can actually signal the start of menstruation from one woman to another.

It is important to note that menstrual cycle length can vary and can also be affected by some factors such as hormonal changes and stress. So the chances are two women who spend time together will have an occasional menstrual cycle that starts within a few days apart. This is purely by chance.

Research over the last few years has neither confirmed nor completely written off theories about menstrual synchrony so we cannot conclude if it's real or just a myth. The subject of menstrual synchrony is another medical mystery.